The present disclosure relates to nano electronic devices, in particular, to carbon nanotube (CNT) based electronic devices.
After more than 40 years rapid development, silicon-based transistors are reaching their physical limitations. The state of art 45 nm technology has adopted high-K technology and metal gate electrode to replace SiO2 dielectric and high-level doped polysilicon electrode. The most important part in device, silicon channel, is also gradually replaced by stress silicon. Although the development of 32 nm technologies is nearly over, it is unclear how micro-electronics will develop beyond 32 nm technologies. The transistor technology roadmap of Intel Corporation includes CNT and semiconductor nanowires as candidates for integrated circuits after 2011. But details and feasibilities of these potential technologies are still not available.
As a semiconductor material, silicon does not have the most outstanding performance. Germanium, for example, has s electron mobility much higher than silicon's. Another significant drawback for silicon is that silicon is an indirect-gap semiconductor, which severely limits the development of silicon based devices in photoelectric applications and results in separate development of silicon based integrated circuits (IC) and semiconductor photoelectric device. Although several breakthroughs have been achieved on silicon based photoelectric device in recent years, the integration of silicon based photoelectric device and CMOS device are still not possible due to the differences in their physical dimensions.
CNT is different from silicon in nature. The CNT has advantageous electric properties. The energy band is symmetric at the Fermi level such that electrons and holes have the same mobilities. CNT's electron mobility measured in lab is higher than those in silicon, III-V semiconductor materials such as GaAs, and II-IV semiconductor materials. The hole mobility of CNT is measured to be greatly higher than semiconductor materials. For this reason CNT may be a suitable material for CMOS electric devices. Additionally, the CNT also has beneficial photoelectric properties. CNT has direct band gap. The gap is inversely proportional to the diameter of a carbon nanotube. The band gap for CNT with an approximately 1 nm diameter is in the infrared range, which is ideal to be used as a photoelectric material in communication devices.
There is therefore a need for a more compact and higher performance photoelectric device that does not suffer from the drawbacks of the silicon based semiconductors. There is also a need for a photoelectric device that is integrated with an integrated circuit.